This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Mycobacterium tuberculosis (MTB) contains 11 predicted eukaryotic-like serine/threonine protein kinases (STPKs). Signal transduction mediated by PknB, an MTB STPK, regulates cell shape, and possibly cell division. In this study, we will examine the significance of the highly conserved PknB dimerization interface, which is located on the side opposite the active site. Initial structural determination of a dimerization interface mutant (L33D) showed a monomer which was missing critical catalytic contacts, and mass spectrometry indicated less phosphorylation than wild-type PknB. Additionally, preliminary biochemical data suggests that PknB autophosphorylation is enhanced by dimer formation and that this process is intermolecular. To further characterize the activation mechanism of PknB, we are interested in determining the crystal structures of the inactive kinase using a catalytically dead mutant (D138N) alone, and in combination with the dimer interface mutation. We also hope to obtain higher-quality atomic resolution data for the L33D structures. These studies will further define the regulatory mechanisms of STPKs and aid in the development of novel MTB therapeutics.